Fire protection containers incorporating novel low free water insulation materials

ABSTRACT

The present invention contemplates water-bearing silicate materials achieved by modifying the basic method of essentially reacting water glass with calcium chloride to bind the free water into solid form without adversely affecting the basic chemical and physical structure of the original product. The material is then dried by using a wicking agent, such as cellulose sponge, adding an anhydrous salt to the material to form a crystalline hydrate, or adding calcium oxide or calcium hydroxide to the material to form a microstructure that physically retains the water. The material is then incorporated into a fire protection contained in which the material forms the outermost wall of the container, a light-weight porous material such as urethane foam and intermediate layer, and a phase change material with a melting point of about 70 degrees F. to 125 degrees F. forms the innermost wall.

REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of application Ser. No.09/760,426, filed Jan. 12, 2001 now U.S. Pat No. 6,841,209, which claimspriority to U.S. Provisional Application Ser. No. 60/175,774, filed Jan.12, 2000.

BACKGROUND

Portions of the present application have been partially disclosed in thefollowing Disclosure Document which is incorporated herein by reference:

Advanced Slow-Curing Fire Protection Materials, Disclosure Document No.462049, dated Sep. 19, 1999.

1. Field of Invention

The present invention relates to fire protection containers such assafes, storage boxes, filing cabinets, and other related applications,and to improved insulation materials incorporated therein.

2. Background of Art

Co-Pending application by Applicant describe a novel water-basedsilicate insulation material which has been used by Thermal Sciences,Inc. for production of fire protection containers under the FireCoolertrademark. The material is essentially produced from a combination ofsodium silicate solution with a high silica to soda ratio (about 3 to 4,i.e., commercial water glass) and a polyvalent metal salt such ascalcium chloride. These components react to form a wet solid. Althoughit has been shown to outperform virtually all other known fireprotection insulation compositions in its class, the material can bedifficult to handle due to the fact that is comprises a fairly largepercentage of non-chemically bound water which can leach from defects inthe container walls.

Currently used compositions utilize a roto-molded plastic shell intowhich the insulation slurry is poured or injected. After curing, waterreleased from the solidified insulation can migrate to and leak frompinhole defects which sometimes occur in the plastic shell. This createssome difficult quality control problems for the roto-molding vendor. Onemanufacturing method that was developed to mitigate the problem involvedthe post-cure insertion of various wicking materials such as cellulosesponge into the insulation fill hole to extract some of the free-water.This did not adversely affect the fire protection performance of theinsulation. However, the additional manufacturing step adds toproduction costs and is a very slow process which can require up toseveral days to complete.

It is therefore, highly desirable to create an improved insulationformula which is dry (or at least contains a minimal amount of unboundwater) on cure and which provides the same fire protection as the parentmaterial. In order to maintain the essential chemical composition andstructure of the original insulation, free water reduction has to bebased on chemically or physically binding the water in a way that isindependent of the basic reactions that form the parent material. Theadditives used to reduce free water also tend to increase the rate atwhich the insulation slurry sets up, thus making it more difficult tomix and pour in large quantities. Thus, methods to counteract thisundesirable side effect are also desirable.

3. Objects and Advantages

It is a principal object and advantage of the present invention toprovide modified formulations of the aforesaid parent material whichpreserve all of its original fire protection properties and which makethe material essentially dry in the cured state.

Another object and advantage of the present invention is to offermanufacturing methods that facilitate an increase in the set-up time ofthe insulation slurry while maintaining its desirable properties.

An additional object and advantage of the present invention is toprovide a fire protection storage container utilizing the improvedinsulation materials.

Other objects and advantages of the present invention will in part beobvious, and in part appear hereinafter.

SUMMARY OF THE INVENTION

In accordance with the foregoing objects and advantages, the presentinvention contemplates water-bearing silicate materials for fireprotection which are essentially dry when cured. The dryness property isachieved by modifying the basic method of essentially reacting waterglass with calcium chloride in such a way as to bind the free water intosolid form without adversely affecting the basic chemical and physicalstructure of the original product. The invention further contemplatesthe incorporation of these materials into one or more fire protectioncontainer configurations such as a multilayered structure in which theinsulation forms the outermost wall of the container, an intermediatelayer comprising a light weight porous, thermal insulator such asurethane foam, and an innermost layer comprising a phase change materialwith a melting point of around 70 degrees F to 125 degrees F, dependingon the heat bearing characteristics of the objects to be protected.

Besides the aforementioned method of drying the insulation material byphysically wicking the excess water from the cured parent materialthrough use of a sponge-like material, two other methods have beendeveloped to bind the free water in the insulation material. The firstof these includes the addition of an anhydrous salt to the slurry toform a crystalline hydrate. Dibasic sodium phosphate (NA2HP04) workseffectively for this purpose. The second method includes the addition ofcalcium oxide or calcium hydroxide to the slurry. This converts solubleand/or colloidal silica (SiO2) present in the mixture to calciumsilicate (CaSiO3), thereby resulting in a material microstructure whichprovides more effective physical retention of the water. This secondmethod is assisted by the formation of calcium metasilicate dehydrate(CaSiO3 2H2O) resulting from the additional CaSiO3 produced. Thefollowing reactions take place in the above methods:

-   -   1) Starting with Calcium Oxide CaO+H2O to Ca(OH) 2    -   2) Starting with Calcium Hydroxide Ca(OH)2+2NaCl to CaCl2+2NaOH        2NaOH+SiO2 to Na2SiO3+H2O CaCl2+Na2SiO3 to CaSiO3+2NaCl        Na2SiOJ(SiO2)x+CaCl2 to 2NaCl+CaSiOJ(SiO2)x        Note that NaCl is present as a byproduct of the reaction of the        parent material components.

It has also been found that it can be helpful to increase the sodiumsilicate content of the mixture without also adding water (as would bepresent with the addition of more sodium silicate solution) by includinga partially hydrated (easily soluble) sodium silicate powder into theslurry. An example of this would be spray-dried sodium silicate soldunder the name BriteSil by the Philadelphia Quartz Corporation.

Either one or a combination of the above-methods, the incorporation ofeither of either anhydrous Dibasic Sodium Phosphate and/or Calcium Oxideor Calcium Hydroxide into the slurry comprising the components of theparent material formulation can be used to produce the dry fireprotection insulation material of the present invention. All result inmaterials with excellent fire protection performance. The only drawbackis that the first method (adding dibasic sodium phosphate) can cause adimensional instability problem in which the material expandsunpredictably by several percent over a period of several days aftercuring. This could be the result of the dibasic sodium phosphateshifting between different states of hydration with a resultant changein crystalline structure. Therefore, this method should only be employedwhen this post-expansion can be accommodated without physicallydeforming the walls of the container. Thus, it should be pre-cast, curedand allowed to expand, and then covered with an outer shell that formsthe actual product exterior surface. Thus, this formulation would not bewell-suited to a product design in which the slurry is to be poured intoa roto-molded plastic shell, for example. The above methods (such as theaddition of calcium oxide or calcium hydroxide) further reduce thematerial set-up time, making it more difficult to mix and pour.

In an effort to increase the material set-up time without adverselyaffecting the desirable properties such as fire resistance, structuralintegrity and dryness on curing, the present invention optionallyincludes the addition of a small quantity of one or more water solubleorganic materials to the insulation mixture. The additives shouldpreferably be mixed thoroughly into the water glass first, with thesolids (calcium chloride, calcium oxide, etc.) then added and mixed into form the slurry. The additive may comprise about 1 to 8 percent ofthe total weight of the final product (preferably no more than about 2to 4 percent). These materials do not form reaction products with theother components of the mixture and do not alter the chemical orstructural properties of the cured insulation. The intent behind the useof these additives is to reduce the solubility and mobility of the otherreactants to increase the time it takes for the reaction products toform and to slow the subsequent crystallization/solidification thatcreates the final product.

Three readily available candidate materials have been tested withpositive results. This would seem to indicate that the concept is validfor most all water soluble organics. However, it is known that certainones, such as low molecular weight alcohols (i.e. ethyl and methylalcohol), may not be practical because they tend to form insoluble gelswhen they are mixed with the water glass. Other polar compounds such asethylene and propylene glycol also tend to cause some gelling, but thesegels dissolve with further mixing causing the formation of a homogenous,although slightly higher viscosity, water glass mixture. Both ethyleneand propylene glycol have been tested and work well in the presentinvention. However, propylene glycol is preferred because of its lowtoxicity as compared to ethylene glycol. A water soluble oil (sold foruse as a cutting oil for machining metals) was also tested with goodsuccess. As expected, the water soluble oil mixed very easily into thewater glass with no gelling. Examples of material formulations testedare shown in the Detailed Description below.

The mixing time (time elapsed before the slurry begins to set up andthicken to the point where it can no longer be poured) whenincorporating these additives ranged from about 5 minutes to as long as15 to 20 minutes for sample sizes of about 1.5 pounds. By comparison,each of the formulations tested would have had a mixing time of about 1to 3 minutes without the presence of the water soluble organic additive.Although it is believed that a very large number of individual watersoluble organic compounds and combinations thereof could be successfullyused in the present invention, only a few have been tried at the presenttime. These include ethylene glycol, propylene glycol, and a watersoluble machining/metal cutting oil (brand name Rust-Lick WS-5050, HeavyDuty water Soluble Oil, made by ITW Devcon Corp.) The latter contains anumber of components such as tripropylene glycol, chlorinated olefins,and modified petroleum distillates. The above additives are apparent ina number of the example material formulations shown below. Note that inall formulations, the water soluble organic additive was firstthoroughly mixed into the water glass; the solids (solids are premixedwith each other) are then mixed in to the water glass to form theinsulation slurry.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a fire protection containerillustrating its multiple layers.

DETAILED DESCRIPTION

Referring now to the drawing FIGURE, the cross-section of a fireprotective container, designated generally by reference numeral 10, isillustrated as comprising a compartment 12 in which miscellaneousarticles may be placed that is defined by a mandatory outer layer 14,and an optional intermediate layer 16 and inner layer 18. Outer layer 14is created by first mixing a slurry comprising the components describedin a greater detail hereinbelow, and then casting the slurry to form asolid. The casting method is determined by the specific product designand other manufacturing considerations such as possible post-expansionof the insulation material as described previously.

Although any size fire protection container 10 is conceivable (includingan entire room or building) with any fire duration rating (andcorresponding wall thickness), the following disclosure is be based onexisting product requirements relating to a file drawer sized box with afire duration capability of about 1 to 2 hour fire exposure with a 3 to10 hour cool-down period. For this sized container, outer wall 14 is ofa thickness of about 1 to 2 inches. This alone will generally besufficient for the protection of paper and other items which canwithstand temperatures of up to about 230 degrees F.

Intermediate and inner layers 16, 18 maintain low internal containertemperatures at around 125 to 70 degrees F for the protection of moreheat sensitive items such as magnetic and optical date storage media andcertain photographic materials, for example. For this purpose,intermediate layer 16 is generally about 0.5 to 2 inches thick andcomposed of urethane, polystyrene foam, or a similar material. Innerlayer 18 is around 0.25 to 1 inch thick and composed of a high heatcapacity phase change material which has a melting point at or near thedesired maximum internal container temperature. A preferred phase changematerial is comprised of a combination of dibasic and tribasic sodiumphosphate (Na2HPO4, Na3PO4), water, and optionally, a lesser amount ofsodium silicate solution (a commercial grade of water, glass, forexample). As previously indicated, these phase change formulations willmaintain internal container temperature in the range of about 70° to125° F. under the conditions stated above.

Examples of phase change formulations currently tested are; in parts byweight (Water; 154, Na₂HP0₄ anhydrous; 100, Na₃P0₄.12H₂0; 70), (WaterGlass; 4, Water; 13.14, Na₂HP0₄ anhydrous; 10, Na₃P0₄.12H₂0; 3.86,“Impurity”; 0 to 3), (Water Glass; 4, Water; 8, Na₂HP0₄ anhydrous; 10,Na₃P0₄.12H₂0; 10, “Impurity”; 0 to 3). The “Impurity” shown in the abovecan be anyone of a number of water soluble salts wherein either or bothof the anion or cation are chosen to be substantially different from theother components of the mixture (i.e., in terms of atomic/molecularweight). The purpose of this is to help prevent a potential postexpansion of the cooled/solidified phase change material similar to whathappens when Na2HP04 is added to the fire-protection insulation materialas described hereinbefore.

The slurry that composes outer layer 14 is produced by mixing togetherthe components listed in the following examples. The solids shouldgenerally be added to the water glass solution and mixed thoroughly fora period of about 10 to 60 seconds. The slurry is then injected orpoured into the appropriate mold or shell (i.e., a roto-molded plasticshell) and allowed to fully set and cure.

EXAMPLES

The Water Glass in all of the following compositions is generally acommercial grade sodium silicate solution which is about 40% solids, 60%water, and has a SiO₂:Na₂O ration of about 2:1 to 4:1 (in the range ofabout 2 to 4, and preferably about 3.2). Some specific examples are:

Amount Component in parts by weight 1) Water Glass 56 CalciumMetasilicate 0 to 2  Dibasic Sodium Phosphate 6 to 12 (Na₂HP0₄anhydrous) Calcium Chloride (monohydrate) 5 to 8  or dehydrate form;flake or granular particles, size about 2 to 5 millimeters) PropyleneGlycol and/or Water-Soluble Oil 0 to 3  2) Water Glass 56 Spray-driedSodium Silicate (BriteSil) 0 to 12 (SiO₂:Na₂O ratio about 2 to 3.5)Calcium Oxide and/or Calcium Hydroxide 4 to 10 Calcium Chloride (typesame as above) 2 to 10 Propylene Glycol and/or Water-Soluble Oil 0 to 3 3) Water Glass 56 Spray-dried Sodium Silicate 0 to 12 (type same asabove) Calcium Oxide and/or Calcium Hydroxide 2 to 10 Dibasic SodiumPhosphate (Anhydrous) 4 to 12 Calcium Chloride (type same as above) 2 to10 Propylene Glycol and/or Water-Soluble Oil 0 to 3  4) Water Glass 20Ethylene Glycol 1 Calcium Oxide 2 Calcium Chloride 3.2 MIXING TIME: 5minutes 5) Water Glass 20 Ethylene Glycol 2 Calcium Oxide 2 CalciumChloride 3.2 MIXING TIME: 7 minutes 6) Water Glass 20 Propylene Glycol1.2 Calcium Oxide 2 Calcium Chloride 3.2 MIXING TIME: 7 to 8 minutes 7)Water Glass 20 Propylene Glycol 1.2 Calcium Oxide 2 Calcium Chloride 2.4BRITESIL C24 2 MIXING TIME: 12 minutes 8) Water Glass 20 PropyleneGlycol 1.2 Calcium Oxide 2 Calcium Chloride 2.4 MIXING TIME: 12 minutes9) Water Glass 20 Propylene Glycol 1.2 Calcium Oxide 2.5 CalciumChloride 2.4 MIXING TIME: 5 to 7 minutes

The Propylene Glycol used was an automotive coolant brand mixed 50/50with water.

BRITESIL C24 is a spray-dried, highly water soluble sodium silicatepowder made by the PQ Corporation.

10) Water Glass 20 Water Soluble Oil 1 Calcium Oxide 2 Calcium Chloride3.2 MIXING TIME: 13 minutes 11) Water Glass 20 Water Soluble Oil 1Calcium Oxide 2 Calcium Chloride 2.4 MIXING TIME: 20 minutes 12) WaterGlass 20 Water Soluble Oil 1 Calcium Oxide 3 Calcium Chloride 2.4 MIXINGTIME: 5 to 6 minutes 13) Water Glass 20 Water Soluble Oil 1 CalciumOxide 2.5 Calcium Chloride 2.4 MIXING TIME: 10 to 12 minutes

Each of these examples produces an outer layer 14 having superbinsulation properties to protect the contents of container 10 from heatand fire, and which is essentially dry in a cured state.

1. A fire protective container, comprising: a. an outer wall consistingessentially of: i. water glass composed of a sodium silicate solutionthat is about 40% solids, 60% water, and having a SiO2:Na2O ratio in therange of about 2:1 to 4:1; ii. calcium chloride; and iii. an additivechosen from the group of calcium oxide or calcium hydroxide.
 2. The fireprotective container of claim 1, further comprising: a. an intermediatewall; and b. an inner wall composed of a phase change material.
 3. Thefire protective container of claim 2, wherein said outer wall is about 1to 2 inches thick, said intermediate wall is about 0.5 to 2 inchesthick, and said inner wall is about 0.25 to 1 inch thick.
 4. The fireprotective container of claim 3, wherein said intermediate wall iscomposed of urethane.
 5. The fire protective container of claim 3,wherein said intermediate wall is composed of polystyrene foam.
 6. Thefire protection container of claim 1, wherein said outer wall furtherconsists essentially of: a. spray dried sodium silicate; and b.propylene glycol.
 7. The fire protection container of claim 2, whereinsaid outer wall consists essentially of: a. 56 parts by weight of saidwater glass; b. 0 to 12 parts by weight of said spray dried sodiumsilicate; c. 4 to 10 parts by weight of said additive; d. 2 to 10 partsby weight of said calcium chloride; and e. 0 to 3 parts by weight ofsaid propylene glycol.
 8. The fire protection container of claim 1,wherein said outer wall further consists essentially of anhydrousdibasic sodium phosphate.
 9. The fire protection container of claim 8,wherein said anhydrous dibasic sodium phosphate is added in 4 to 12parts by weight.
 10. A fire protection container, comprising: a. anouter wall consisting essentially of: i. water glass composed of asodium silicate solution that is about 40% solids, 60% water, and havinga SiO2:Na2O ratio in the range of about 2:1 to 4:1; ii. calciumchloride; iii. propylene glycol.
 11. The fire protection container,comprising: a. an outer wall consisting of: i. water glass composed of asodium silicate solution that is about 40% solids, 60% water, and havinga SiO2:Na2O ratio in the range of about 2:1 to 4:1; ii. calciumchloride; iii. water soluble oil; and iv. calcium oxide.
 12. The fireprotection container of claim 11, wherein said outer wall consistsessentially of: a. 20 parts by weight of said water glass; b. 1 part byweight of said water soluble oil; c. 2 to 3 parts by weight of saidcalcium oxide; and d. 2.4 to 3.2 parts by weight of said calciumchloride.